The present disclosure provides methods and compositions for removing resin coatings from the surfaces of wellbore equipment and preventing resin from curing in undesirable locations.
Hydrocarbon wells are often located in subterranean zones that contain unconsolidated particulates that may migrate within the subterranean formation with the oil, gas, water, and/or other fluids produced by a well penetrating the subterranean formation. As used herein, the term “unconsolidated particulate,” and derivatives thereof, includes loose particulates and particulates bonded with insufficient bond strength to withstand the forces created by the production of fluids through the formation, which may include but are not limited to formation fines and/or proppant particulates. “Formation fine(s),” another term used herein, refers to any loose particles within the portion of the formation, including, but not limited to, formation fines, formation sand, clay particulates, coal fines, and the like. A similar situation can exist in certain wells where particulates referred to as “proppant particulates” may be introduced into the subterranean formation. The proppant particulates may be used in conjunction with hydraulic fracturing to prevent the fractures from fully closing upon the release of hydraulic pressure, forming conductive channels through which fluids may flow to the wellbore.
The presence of these unconsolidated particulates in produced fluids is often disadvantageous and undesirable in that the particulates may abrade pumping and other producing equipment and reduce the fluid production capabilities of producing zones. Unconsolidated subterranean zones include those that contain loose particulates and those wherein the bonded particulates have insufficient bond strength to withstand the forces produced by the production of fluids through the zones. “Zone” as used herein simply refers to a portion of the formation and does not imply a particular geological strata or composition.
One way to address the disadvantages caused by unconsolidated particulates is to introduce a resin into the unconsolidated subterranean zone. The resins used in these types of applications may comprise any of numerous types of polymerized synthetics or chemically modified natural resins including thermoplastic materials and thermosetting materials. In addition to maintaining a relatively solids-free production stream, consolidating particulates also aids in protecting the conductivity of the formation. Such consolidation treatments involve the injection of a resin in liquid form into the formation and thereafter causing the resin to cure to an infusible state known as thermosetting. The cured resin cements the sand grains or other unconsolidated particulates together by providing high strength, and, ideally, retaining high percentage of initial formation permeability (“Regain Permeability”).
One disadvantage associated with using curable resins is the removal and clean up of the resin from equipment used in placing the resin. For example, a residue of resin may remain on fracturing equipment used during fracturing operations. This includes, but is not limited to, connecting hoses, valves, sand hoppers, sand screws, blender tubs, and the like. Without proper cleaning or removal, there is potential that a layer of resin may build up each time the equipment surface is exposed to the resin. The buildup of resin could result in plugging of equipment or causing the equipment not to function properly. Moreover, particulates, such as sand or proppant, may become entrapped within the resin and lead to further equipment damage
The current clean-up solutions depend on the use of glycol ether type mutual solvent to thin down and remove the coated resin. This type of mutual solvent is currently considered toxic in many parts of the world. Moreover, in some areas of the United States, glycol ether mutual solvents cannot be used in well treatments or in the cleaning of equipment after being exposed to curable resins or tackifying agents.